Spindle device having a dynamic-pressure-fluid bearing

Abstract

In a spindle device mounted to a disc driving apparatus, a mist seal which blocks a mist of lubricating fluid, an oil seal which prevents the lubricating fluid from flowing out, and an oil pool which prevents surplus fluid from flowing out, are combined and disposed so that the lubricating fluid from a dynamic-pressure-fluid bearing is prevented from flowing out or splashing into a clean space. As a result, inconveniences such as a head crush or a head absorption can be avoided, and a reliable spindle device is realized.

What is claimed is:  
     
       1. A spindle device comprising: 
       a bracket;  
       a shaft fixed to said bracket;  
       a stator core mounted to said bracket and having a coiled wire;  
       a sleeve rotatively supported by said shaft via lubricating fluid so as to form a radial-dynamic-pressure-fluid bearing, said sleeve having first and second end faces;  
       a hub fixed to said sleeve and adapted to receive discs thereon in a disc space;  
       a rotor magnet mounted to said hub and situated opposite to said stator core;  
       a magnetic shield panel disposed on an inner circumference of said hub and facing said stator core; and  
       an oil pool disposed between said sleeve and said magnetic shield panel.  
     
     
       2. The spindle device according to claim  1 , and further comprising a rotor frame disposed on an inner circumference of said hub and facing said stator core. 
     
     
       3. The spindle device according to claim  2 , wherein said rotor frame supports said rotor magnet. 
     
     
       4. A spindle device comprising: 
       a shaft having a first end and a second end;  
       a stator;  
       a rotor rotatably supported by said shaft via lubricating fluid so as to form a radial-dynamic-pressure-fluid bearing;  
       a magnet opposed to a coiled wire for causing rotation of said stator relative to said rotor; and  
       a mist-proof seal means to create a mist-proof seal adjacent said first end of said shaft for preventing a mist of lubricating fluid from flowing beyond said first end of said shaft.  
     
     
       5. The spindle device according to claim  4 , and further comprising a bracket, wherein said shaft and said stator are fixed to said bracket. 
     
     
       6. The spindle device according to claim  5 , wherein said rotor comprises a sleeve rotatably supported by said shaft via the lubricating fluid so as to form the radial-dynamic-pressure-fluid bearing, and a hub fixed to said sleeve, with said hub being adapted to receive discs thereon in a disc space, and wherein said means to create the mist-proof seal is to create the mist-proof seal for preventing mist of the lubricating fluid from flowing beyond said first end of said shaft and into said disc space. 
     
     
       7. The spindle device according to claim  6 , wherein said stator includes a core having said coiled wire thereon, and said magnet is secured to said hub. 
     
     
       8. The spindle device according to claim  7 , wherein said sleeve has a first end face and a second end face, and further comprising a thrust-dynamic-pressure-fluid bearing including a rotary thrust ring disposed on first end face, and a fixed thrust ring fixed to said shaft, and wherein said means to create the mist-proof seal is disposed between said thrust-dynamic-pressure-fluid bearing and the disc space. 
     
     
       9. The spindle device according to claim  4 , wherein said means is to create the mist-proof seal by creating a viscous seal. 
     
     
       10. The spindle device according to claim  9 , wherein said means to create the viscous seal by creating sufficient air pressure to prevent the mist of the lubricating fluid from flowing beyond said first end of said shaft. 
     
     
       11. The spindle device according to claim  10 , wherein said means to create the sufficient air pressure includes a helical groove in an inner surface of said rotor surrounding said first end of said shaft, such that rotation of said rotor causes said helical groove to rotate whereby air is caused to flow from beyond said first end of said shaft toward the radial-dynamic-pressure-fluid bearing. 
     
     
       12. The spindle device according to claim  11 , wherein said rotor includes an annular member attached thereto, and said helical groove is in an inner circumferential surface of said annular member. 
     
     
       13. The spindle device according to claim  12 , and further comprising an oil pool disposed between said rotary thrust ring and said helical groove, and wherein said shaft includes a groove adjacent said oil pool. 
     
     
       14. The spindle device according to claim  13 , and further comprising a bracket, wherein said shaft and said stator are fixed to said bracket. 
     
     
       15. The spindle device according to claim  14 , wherein said rotor comprises a sleeve rotatably supported by said shaft via the lubricating fluid so as to form the radial-dynamic-pressure-fluid bearing, and a hub fixed to said sleeve with said annular member attached to said hub, wherein said hub is adapted to receive discs thereon in a disc space, and wherein during the rotation of said hub said helical groove causes the air to flow from beyond said first end of said shaft such that the mist of the lubricating fluid is prevented from flowing beyond said first end of said shaft into the disc space. 
     
     
       16. The spindle device according to claim  15 , wherein said stator includes a core having said coiled wire thereon, and said magnet is secured to an inner circumferential surface of said hub. 
     
     
       17. The spindle device according to claim  16 , wherein said sleeve has a first end face and a second end face, and further comprising a thrust-dynamic-pressure-fluid bearing including a rotary thrust ring disposed on said first end face of said sleeve, and a fixed thrust ring fixed to said shaft and opposing said rotary thrust ring, and wherein said helical groove is disposed between said thrust-dynamic-pressure-fluid bearing and said first end of said shaft. 
     
     
       18. The spindle according to claim  17 , wherein said shaft includes a screw threaded into said first end of said shaft, wherein said groove adjacent said oil pool is formed in said screw, and wherein said helical groove surrounds said screw. 
     
     
       19. The spindle device according to claim  17 , and further comprising a centrifugal force seal disposed on an outer circumferential surface of said sleeve. 
     
     
       20. The spindle device according to claim  17 , and further comprising a mount collar fixed to said bracket and coaxially surrounding said second end face of said sleeve. 
     
     
       21. The spindle device according to claim  4 , wherein said means to create the mist-proof seal includes a ring-shaped magnet, a pair of ring-shaped magnetic members sandwiching said ring-shaped magnet, and a magnetic fluid. 
     
     
       22. The spindle device according to claim  4 , wherein said means to create the mist-proof seal comprises a labyrinth seal including a small clearance between an inner circumference of said rotor and an outer circumference of said rotor.